scope:

This part specifies methods for measuring beam widths (diameter), divergence angles and beam propagation ratios of laser beams. This part is applicable to general astigmatic beams or unknown types of beams. For stigmatic and simple astigmatic beams, Part 1 is applicable. Within this part the description of laser beams is accomplished by means of the second order moments of the Wigner distribution rather than physical quantities such as beam widths and divergence angles. However these physical quantities are closely related to the second order moments of the Wigner distribution.